The present invention relates to a folding apparatus having at least one conveyor belt which is used to convey signatures at least on a section of a path of the signatures through the folding apparatus.
In a folding apparatus, sheets or copies that are cut off from a printing-material web are folded into signatures and delivered. For that purpose, typical folding apparatuses have a plurality of processing devices to produce folds, perforations, grooves, cuts, and the like. Folding apparatuses often have a number of paths along which the processing devices are arranged and the signatures are transported. Frequently, transport devices are designed as conveyor belts. Depending on the final printed product to be produced or the type of fold, it is possible to switch between the different paths. For simplicity, a cut-off sheet or a cut-off copy will be referred to herein as a signature.
Due to the complex sequence of operations carried out on the signature, folding apparatuses contain a plurality of error sources causing damage to the signatures or a loss of production. These error sources in particular also may arise when setting up the folding apparatus in a new configuration for a final printed product to be produced or a type of fold to be produced. Thus, in typical folding apparatuses of the prior art, provision is made for monitoring devices for the transport of the signatures along the different paths in order to detect paper jams and misdirection of paper.
For example, European Patent Application No. 1 069 062 A2 provides a paper travel monitoring device in a folding apparatus, the paper travel monitoring device being able to detect misdirected signatures and to turn off the folding apparatus. Arranged along the paths of the signatures through the folding apparatus are sensors which are evaluated on the basis of the signature progression. Preferably, the sensor system is composed of sensor pairs, that is, transmitters and receivers between which runs the path of the copies.
It has turned out that an important reason for a loss of production in the folding apparatus is the unexpected breakage of conveyor belts, which are subject to pronounced wear. Since in known methods heretofore monitoring devices concentrate on the paper travel per se, in particular for the adjustment of the folding apparatus, or detect paper jams or misdirection of paper after a problem has occurred, so far information on the condition of the conveyor belts in the folding apparatus is not provided to the machine control during set-up or while the production is in progress. Normal wear, the unexpected breaks and an unfortunate overstretching because of a paper jam or due to an emergency stop of the machine or even the disappearance of a conveyor belt because of the exceeding of its service life are only detected during a visual inspection of the folding apparatus by a machine operator, typically while the folding apparatus is at rest. Furthermore, a poor quality condition of the conveyor belts can result in damage to the signatures even prior to breakage.